Rhoophilus is morphologically similar to the Holarctic inquiline genera Synergus, Saphonecrus, and Synophrus, all of which typically attack oak cynipid galls. The transverse ridges of the mesoscutum, and a mesopleuron sculptured with longitudinal ridges in Rhoophilus closely resemble characters in several species of the Synergus/Saphonecrus complex. A sister group relationship between Rhoophilus and these three oak inquiline genera was hypothesized by Ronquist (1994) and Liljeblad and Ronquist (1998).

Rhoophilus has a closed marginal cell, a character shared with Qwaqwaia. The areolet is triangular as in Phanacis, but larger and more distinct, whereas it is elongate rhomboidal in Qwaqwaia. Rhoophilus lacks an occipital carina as in Phanacis (present in Qwaqwaia), but has tergites 2 and 3 fused, whereas these are free in Phanacis.

South Africa: Western, Eastern and Northern Cape Provinces.

Inquiline forming secondary cells in galls induced by Scyrotis moths (Cecidosidae) on Searsia (formerly Rhus) (Anacardiaceae) shrubs and trees. The larval cells expand into the hollow interior of the host gall resulting in death of the gall inducing moth larva (van Noort et al. 2007).

Rhoophilus loewi Mayr, 1881 (South Africa)